UNIVERSITY    OF    CALIFORNIA     AGRICULTURAL    EXPERIMENT  STATION 
COLLEGE   OF  AGRICULTURE  "NJ-  'DE  WHEELER"  '■«'"■" 

THOMAS    FORSYTH    HUNT,    Dean  an d  Director 

BERKELEY 


E.    VAN    NORMAN,    Vice-Director    and    Dean 
University  Farm  School 


CIRCULAR  No.  191 
January,  1918 


PRUNING  THE  SEEDLESS  GRAPES 


By  FREDERIC  T.  BIOLETTI 


The   general   principles   of   vine    pruning;   are    the   same    for    all 
varieties.     These  and  the  general  practice  of  pruning  have  been  quite 


Fig.   1. — Forms  of  cuttings. 


fully  discussed  in  Bulletins  241  and  246  of  this  Station.  In  this 
circular  will  be  given  simply  specific  directions  for  the  methods  of 
pruning  which  have  given  the  best  results  with  seedless  raisin  grapes. 


1.   TREATMENT   OF   YOUNG    VINES 

First  Year. — Cuttings  are  made  12,  15,  or  18  inches  long;  the 
shorter  for  nursery  planting  or  moist  soil ;  the  longer  for  planting  in 
the  vineyard  and  where  the  soil  lacks  moisture  (see  Fig.  1).  Well- 
grown  and  well-ripened  laterals  make  better  cuttings  than  over-grown, 
long- join  ted  canes. 


Fig.  2. — Pruning  of  rooted  vine  before  planting. 


One-year-old  rooted  vines  are  pruned  to  one  cane,  which  is 
shortened  to  one  or  two  buds.  Surface  roots  are  cut  off  entirely  and 
the  lower  roots  shortened  to  1  to  4  inches,  according  to  size  (see 
Fig.  2).  When  planted,  only  the  buds  at  the  top  are  left  above 
ground. 

During  the  first  growing-season  (see  Fig.  3),  little  pruning  is 
done.  With  vines  on  resistant  stocks,  the  stock  suckers  and  scion 
roots  must  be  carefully  cut  off  clean.  The  removal  of  surface  roots 
is  also  advisable  in  irrigated  land. 


In  the  first  winter  following  planting,  the  vines  (see  Fig.  4a)  are 
pruned  to  one  cane,  and  this  cane  is  shortened  to  two  buds,  exactly 
as  was  done  with  the  young  vine  before  planting  (see  Fig.  4b).  The 
vines  are  then  staked.  The  stakes  used  are  only  temporary  and  need 
not  be  more  than  three  feet  long  and  an  inch  and  a  half  in  diameter. 


■3 

S^sJ 

itasn     l**^£ 

-'  ^fflum 

j 

mmjBk^m  W 

_-— JUM.""                    \  \ 

5!^^^5™! 

Fig.  3. — Growth  during  the  first  summer. 


They  should  be  driven  about  two  inches  from  the  vine  on  the  leeward 
side  so  that  the  prevailing  winds  will  press  the  growing  vine  against 
the  stake. 

Second  Year. — During  the  second  growing-season,  the  vines  need 
careful  and  continual  attention.  Though  only  two  well-defined  buds 
have  been  left,  many  shoots  will  start.  All  but  one  or  at  most  two 
of  these  are  removed  as  soon  as  they  have  grown  one  or  two  inches. 


This  throws  the  energies  of  the  vine  into  those  left,  which  will  there- 
fore grow  rapidly  (see  Fig.  5a). 

As  soon  as  one  of  the  shoots  has  grown  six  to  ten  inches,  it  is  tied 
loosely  to  the  stake,  and  the  other,  together  with  any  new  shoots 


Ml >™ 


Fig.  4. — Vine  at  end  of  first  growing  season.      A,  before  pruning;  c,  c,  Places  for 
making  cuts;  B,  after  pruning  and  staking. 


Fig.  5. — Growth  and  treatment  of  the  vine  during  the  second  season,     c,  c,  Place 
where  shoots  are  removed;  L,  L,  laterals. 


which  have  started,  are  removed  at  the  same  time  (see  Fig.  56). 

The  single  shoot  will  then  grow  rapidly  and  must  be  tied  again 
higher  (see  Fig.  5c.) 

When  the  shoot  has  grown  one  or  two  feet  above  the  top  of 
the  short  stake,  it  is  topped  at  about  three  feet  from  the  ground 
(see  Fig.  5c). 


This  will  force  a  growth  of  laterals  (see  Fig.  od).  If  these  laterals 
grow  so  large  that  they  are  in  danger  of  being  broken  by  the  wind, 
they  should  be  topped  or  pinched.  All  snckers  from  below  ground 
should  be  carefully  removed  as  soon  as  they  appear. 


*iV 

| 

1 

A.  Average  vine.  B.  Very  vigorous  vine. 

Fig.  6. — Winter  pruning  second  year. 

The  second  winter  pruning  will  be  very  simple  if  the  summer 
work  has  been  done  properly.  It  consists  in  cutting  back  the  single 
cane  to  a  height  of  about  eighteen  inches  (see  Fig.  6a),  leaving  a  full 
joint  above  the  top  bud.  Where  strong  laterals  have  been  produced, 
those   on  the   upper  part  of   the   cane   should  be   cut  back  to   one 


■ 


or  two  buds  and  the  rest  removed  (see  Fig.  6b).  All  the  buds  on 
the  vine  at  this  stage  may  be  fruit  buds  and  a  good  crop  should  be 
produced  in  the  following  autumn.  Vines  which  have  not  made 
eighteen  inches  of  vigorous,  well-ripened  cane  should  be  cut  back  to 
two  buds  and  treated  as  during  the  previous  year.  If  any  vines 
have  been  allowed  to  grow  more  than  one  cane,  all  should  be  removed 
entirely,  except  the  strongest  and  best  placed. 

After  pruning,  the  vines  are  carefully  tied  to  the  stake  as  shown 
in  figure  6.  Extra  heavy  binding  twine  is  good  for  this  purpose. 
The  cane  is  tied  firmly  to  the  stake  by  passing  a  ' '  half -hitch ' '  around 


Fig.  7. — Growth  and  treatment  of  the  vine  during  the  third  season.     T,  T,  places 
where  the  vine  is  tied;  c,  c,  shoots  and  tips  removed;  B,  B,  blossom  branches. 


the  joint  above  the  top  bud.  One  or  two  ties  are  then  made  near  the 
middle  of  the  cane.  These  should  be  moderately  loose  to  allow  for 
growth  of  the  cane  and  should  not  pass  around  the  cane,  or  it  will 
be  choked. 

Third  Year. — As  the  buds  start  in  the  spring,  the  vines  should  be 
gone  over  several  times  and  all  shoots  within  six  to  ten  inches  of  the 
ground  rubbed  off  before  they  are  more  than  two  or  three  inches  long 
(see  Fig.  la).  This  rubbing  off  of  low  buds  will  have  to  be  repeated 
two  or  three  times  (see  Fig.  lb).  This  will  force  all  the  growth  into 
the  upper  shoots  which  will  bear  the  crop  and  form  the  ultimate  arms 
of  the  vine.     When  these  upper  shoots  are  fifteen  to  twenty  inches 


long,  their  extreme  tips  should  be  pinched  off  (see  Fig.  7c).  This 
will  delay  their  lengthening  and  protect  them  from  wind  injury. 
All  suckers  from  below  ground  and  shoots  on  the  lower  part  of  *the 
trunk  should  be  carefully  removed  as  soon  as  they  appear. 


a.  Before  pruning.  b.  After  pruning. 

Fig.  8. — Winter  pruning  third  year — one  fruit  cane  and  two  spurs. 


An  example  of  the  winter  pruning  at  the  end  of  the  third  year 
is  shown  in  figure  8.  It  consists  in  leaving  one  or  more  fruit  canes 
and  two  or  more  wood  spurs.  The  number  of  canes  and  spurs  is 
determined  by  the  size  and  vigor  of  the  individual  vine.  No  invar- 
iable rule  can  be  given.  In  the  example  shown,  there  are  five 
well-developed  canes  on  the  unpruned  vine.     A  vine  having  ten  well- 


8 

developed  canes  should  be  allowed  two  fruit  canes  and  four  spurs. 
This  is  about  the  maximum  for  vines  of  this  age.  The  most  vigorous 
fruit  canes  should  not  be  more  than  four  feet  long  and  those  less 
vigorous  should  be  from  two  to  three  feet.  The  spurs  should  all  have 
two  well-developed  buds,  not  counting  the  base  bud. 

The  spurs  should  always,  whenever  possible,  be  below  the  fruit 
canes,  as  shown  in  the  figure.  They  should  be  so  placed  as  to  give 
the  vine  the  required  shape.  The  position  of  the  fruit  canes  is  less 
important,  as  they  are  removed  the  following  year.  The  spurs  should 
be  arranged  as  much  as  possible  in  the  plane  of  the  trellis  to  be 
erected,  that  is,  spread  out  like  the  ribs  of  a  fan  in  the  direction  of 
the  rows.  This  is  very  important  as  on  the  perfection  with  which 
this  form  is  obtained  depends  the  ease  and  cheapness  of  cultivation 
and  the  protection  of  the  vine  from  cultivation  injuries. 


2.   TRELLISING 

As  soon  as  the  pruning  is  finished,  the  brush  should  be  removed 
and  the  trellis  erected. 

The  trellis  consists  of  two  wires  stretched  along  the  rows  in  the 
direction  where  the  vines  are  closest  together.  The  bottom  wire  is 
placed  at  twenty-four  inches  from  the  ground  and  the  upper  eighteen 
inches  higher.  A  straining  post  is  placed  at  each  end  of  the  row 
and  a  supporting  stake  at  intervals  in  the  row. 

The  stretch  between  posts  should  not  be  much  more  than  200  feet 
and  less  is  better.  A  supporting  stake  every  fifteen  or  twenty  feet 
is  sufficient.  These  stakes  should  be  placed  half  way  between  two 
vines. 

For  straining  posts,  ordinary  fence  posts  may  be  used,  or  4x4 
pieces  of  sawn  redwood  seven  feet  long.  They  may  be  set  in  concrete 
or  held  by  a  stone  or  concrete  anchor  or  by  a  diagonal  brace  of  2  x  4" 
redwood.  For  intermediate  stakes,  the  ordinary  six-foot  split  red- 
wood stakes  are  best.  No.  12  galvanized  iron  fencing  wire  is  most 
commonly  used.  No.  14  is  a  little  too  light,  especially  for  the  lower 
wire.  No.  11  for  the  bottom  wire  and  No.  13  for  the  upper  are  good 
sizes. 

The  general  plan  of  the  trellis  is  shown  in  figure  9.  The  trellis 
should  be  erected  and  the  vines  attached  to  it  before  the  buds  com- 
mence to  swell  in  the  spring.  It  is  best  to  leave  the  temporary  stakes 
to  support  the  vine  for  a  year  or  two  longer,  as  it  is  very  important 
that  the  trunks  should  be  straight  and  perfectly  upright.  Crooked, 
irregular,  spreading  vines  interfere  with  cultivation,  require  a  large 


o 

1 


bo 


B*3 


10 

amount  of  hoeing  and  other  expensive  hand  work,  and  are  subject 
to  injuries  from  the  cultivating  implements,  which  result  in  smaller 
crops  and  shorter  lived  vines. 

All  the  fruit  canes  are  tied  to  the  lower  wire.  The  use  of  the 
upper  wire  is  to  support  the  growing  shoots  during  the  summer  to 
protect  them  from  wind  injury  and' to  keep  the  grapes  off  the  ground. 

The  canes  should  be  looped  over  the  wire  or  turned  once  around 
it.  This  will  prevent  the  weight  of  the  fruit  from  breaking  the  twine 
with  which  they  are  tied  to  the  wire.  They  should  not  be  twisted 
around  the  wire,  for  if  this  is  done,  they  are  very  troublesome  to 
remove  at  the  following  winter  pruning  (see  Fig.  9,  A). 


3.    PRUNING    BEARING   VINES 

In  the  fourth  year,  the  vines  should  be  practically  in  full  bearing, 
and  the  regular  form  of  pruning  for  mature  vines  commences.  This 
consists  in  leaving  two  to  four  fruit  canes  averaging  four  feet  in 
length,  and  four  to  six  renewal  spurs  of  one  to  two  buds  each  (see 
Fig.  9,  B). 

Fruit  Canes. — A  fruit  cane  should  be  of  well-ripened  wood,  of 
good  thickness,  but  not  over-grown.  Any  laterals  with  well-matured 
buds,  which  it  may  have,  should  be  left  and  cut  back  to  short  spurs 
of  one  or  two  buds,  if  not  over  a  third  of  an  inch  thick  and  to  three 
or  four  if  thicker  (see  Fig.  9). 

The  length  of  the  fruit  canes  should  be  from  two  to  five  feet.  The 
thicker  and  more  vigorous  they  are,  the  longer  they  should  be.  They 
should  not  extend  beyond  the  ends  of  the  canes  of  the  next  vine. 

These  rules  will  give  a  maximum  length  of  fruit  wood  for  a  single 
vine  of  about  sixteen  feet.  This  is  ample  for  the  largest  crop  for  a 
vine  in  vineyard  form.  Many  vines  in  the  experiment  vineyard  with 
less  than  this  length  of  fruit  wood  have  borne  80,  90,  and  over  100 
pounds  of  grapes.  Nothing  is  to  be  gained  by  making  the  canes 
longer  or  more  numerous  and  excess  in  this  respect  tends  to  weaken 
the  vine  and  to  prevent  the  production  of  good  fruit  wood  for  the 
following  year. 

It  is  usually  supposed  that  water  sprouts,  that  is,  canes  from  the 
old  wood,  are  not  suitable  for  fruit  canes  and  that  a  fruit  cane  should 
grow  out  of  two-year-old  wood.  Some  limited  tests  with  the  Sultanina 
indicate  that  for  this  variety  at  least,  there  is  little  difference.  How- 
ever, properly  pruned  vines  produce  few  water  sprouts  and  it  is 
nearly  always  possible  to  obtain  all  the  fruit  canes  required  without, 
using  them. 


11 

Renewal  Spurs. — The  renewal  spurs  are  intended  to  produce  canes 
for  the  following  year.  As  some  of  them  may  fail  to  produce  suitable 
canes,  a  few  more  are  left  than  the  number  of  canes  needed.  They 
should,  where  possible,  be  chosen  nearer  the  head  of  the  vine  than 
the  fruit  canes,  in  order  to  prevent  the  vine  from  spreading  too 
rapidly.  No  spurs  should  be  left  which  project  out  into  the  avenues 
at  right  angles  to  the  wire  of  the  trellis.  The  narrow,  fan-shape  of 
the  vine  should  be  carefully  preserved.  Where  spurs  at  right  angles 
to  the  trellis  must  be  left  they  should  be  cut  short  to  the  base  bud. 


Fig.   10. — Unit  of  long  pruning. 


Summer  Pruning. — All  the  seedless  raisin  grapes  are  very  vigorous 
and  summer  pruning  may  be  used  more  freely  than  with  weaker 
vines. 

All  suckers  below  the  ground  and  water  sprouts  from  the  trunk 
below  the  head  should  be  carefully  removed  before  they  become  tough. 

Pinching  the  growing  tips  of  the  shoots  on  the  fruit  canes  when 
they  are  eighteen  to  twenty-four  inches  long  and  the  blossom  bunch 
is  well  formed  helps  the  setting  of  the  fruit  and  increases  the  size  of 
the  berries.  Topping  or  cutting  off  about  twelve  inches  of  the  shoots 
from  the  renewal  spurs  when  they  are  three  or  four  feet  long  promotes 
the  growth  of  laterals  which  give  excellent  fruit  buds  for  the  following 
year. 


12 

The  pruning  of  a  bearing  vine,  in  short,  consists  in  leaving  a 
sufficient  number  of  fruit  canes  to  bear  as  large  a  crop  of  grapes  as 
the  vine  can  bring  to  perfection  without  being  weakened;  in  leaving 
enough  spurs  to  provide  fruiting  wood  for  the  following  season ;  and 
in  having  these  so  placed  that  the  form  of  the  vine  will  be  maintained 
or  improved. 

To  do  this  properly  requires  some  care  and  experience.  Each 
arm,  of  which  there  should  be  from  three  to  four  on  each  vine,  is 
treated  according  to  the  same  principles,  which  are  those  indicated 
in  figure  10. 

This  figure  represents  a  single  well-developed  arm  ready  for  the 
winter  pruning.  F2  is  the  fruit  cane  which  has  just  borne  its  crop. 
Si  is  the  accompanying  renewal  spur.  In  pruning,  the  old  fruit 
cane  is  removed  at  g.  A  new  fruit  cane  (C)  is  formed  from  the 
upper  cane  on  the  old  spur  and  cut  back  to  /  or  fl  or  to  some  inter- 
mediate point,  according  to  its  vigor.  A  lower  shoot  on  the  same 
spur  is  cut  back  to  a  or  lower  to  form  the  new  spur  S. 

This  is  the  normal  treatment  for  a  properly  developed  arm. 
Many  arms  have,  however,  defects  which  make  modifications  of  this 
treatment  necessary.  If  no  good  fruit  cane  has  developed  on  the 
old  spur  Si,  a  fruit  cane  can  be  made  from  one  of  the  canes  on  the 
old  fruit  cane  F2  as,  for  example,  B  or  D.  If  the  arm  is  weak  and 
has  no  good  canes,  a  fruit  cane  should  not  be  left,  but  only  one  or 
two  spurs  as  Rp  and  S.  These  will  produce  little  or  no  crop,  but 
the  arm  will  be  invigorated  and  a  good  crop  will  be  produced  the 
following  season.  If  the  arm  is  becoming  too  long,  like  the  arm 
in  the  figure,  the  renewal  spur  should  be  left  as  near  the  head  of  the 
vine  as  possible  as  at  RP. 

This  method  is  suited  to  all  the  seedless  raisin  grapes,  Sultanina, 
Sultana,  Black  Corinth,  and  White  Corinth.  It  is  also  suitable  for 
any  vigorous  variety  which  requires  long  pruning,  but  must  be  used 
with  discretion,  as  the  vines  will  otherwise  be  weakened  and  after 
one  or  two  good  crops,  they  may  cease  to  bear  or  even  die.  Any 
signs  of  weakening  should  be  followed  by  shorter  pruning,  shorter 
and  fewer  fruit  canes  or  even  no  fruit  canes  at  all  for  one  vear. 


